I used to make two quart of yogurt a day when my kids were home. Of course this was the 60's and 70's, but the best recipe I ever used was one in the old Adelle Davis nutrition books. She would use a can of condensed milk as part of the 2 quarts of milk. I found back then that the best incubator was a diaper bag into which I would put a heating pad set on low, and then the towel wrapped jars of innoculated milk. I usually make it in 2 single quart jars. I just buy it by the quart now from the store as I can't even eat a quart in less than a week.

Would you please confirm my assumption that you left everything in the diaper bag for 24 hours and then refrigerated?

I used to used my gas oven with just the pilot light on but now adays with the electronic ignition it's impossible. Your method sounds perfect... wondering if one of those silver lined hot/cold bags would work the same. Hmmm, might get too warm... maybe with just a towel for cover and not zipped shut.